Figure 3

Possible types of neuropathic disorder. a) Normal motoneuron. b) The sub-threshold injury manifests as a slowing of electrical conduction over the site of compressive lesion and a reduction in axonal transport. Both factors could result in reduced muscle response. c) In the local neurapraxic lesion, conduction is eliminated only over the affected portion of the nerve, and axonal transport is still able to prevent denervation of the muscle. Muscle response is eliminated, since the impulse is blocked at the site of compression. d) The extended neurapraxic lesion describes a case where the axonal transport is even further decreased, and distal nerve portions are no longer able to carry electrical impulses. Demyelination may or may not occur. There is, however, just enough material transported to maintain a connection to the muscle and prevent nerve degeneration. (adapted from McComas et al., 1974 [15]).